1. Field of the Invention
The present invention relates to devices and methods for non-invasively enabling blood circulation to be improved in a more effective manner than existing non-invasive circulatory assistance devices and those which require surgical intervention.
2. Description of Related Art
Current circulatory assistance procedures consist of surgically creating an opening in an artery feeding an organ or a portion of the body and a vein exiting the organ or portion of the body, inserting cannulas, catheters or large needles into the artery and vein, pumping blood at an accelerated rate from the artery through the organ or body portion and returning it to the vein. The blood may be oxygenated or otherwise treated while being circulated extra-corporeally. Such procedures require strict sterility and anti-coagulants, cause damage (hemolysis) to red cells and other blood components and entail the cost and risk of adverse events of surgery.
Some years ago, external counter pulsation or ECP devices were introduced which non-invasively provide circulatory assistance by moving blood from the extremities (legs and buttocks) up to the heart to treat angina pectoris, acute myocardial infarctions (heart attacks) and cardiogenic shock. Early ECP devices employed a liquid, typically water, to compress the extremities. Later ECP devices employed air to compress the extremities, which avoided the need to heat the water to body temperature and the risk of an electrical shock if a balloon or bladder containing the water were to leak or burst. Such early ECP devices are disclosed in U.S. Pat. Nos. 3,288,132; 3,303,841; 3,403,673; 3,734,087 and 3,835,845; as well as co-owned U.S. Pat. Nos. 3,654,919; 3,866,604 and 4,388,919, which, as stated above, are incorporated herein by reference.
Current ECP devices typically include bladders disposed in pockets within each of two pairs of cuffs, which are fastened about the calves and thighs of a person, and two bladders contained in a single cuff which is fastened about his or her buttocks. The bladders are sequentially inflated with air. First, the bladders in the cuffs about the calves are inflated. About 30 to 50 milliseconds later, the bladders in the cuffs about the thighs are inflated, followed, after about 30 to 50 milliseconds, by inflation of the bladders in the cuff about the buttocks inflation and deflation of the bladders is initiated and terminated, respectively, during diastole, after the heart has finished its compression cycle (systole) and is temporarily at rest between compressions (heartbeats). Inflation to a desired pressure is begun after a selected time delay period from the “r” wave of the person's electrocardiogram (ECG), forcing blood up the arteries (and veins) to the heart, counter to the usual direction of arterial blood flow. Compression of the cuffs continues for a selected time period, with simultaneous deflation of all of the bladders occurring during diastole, before the onset of systole, so as not to create resistance to the pumping of blood out of the left ventricle of the heart. When the bladders deflate, the air is released into the atmosphere. Alternatively, the air may be withdrawn by the application of a vacuum to the bladders.
Inflation of the bladders tightens the cuffs and forces blood from the legs and buttocks up the veins into the right heart chambers (auricle and ventricle). This reduces the work-effort of the heart, since a major portion of the heart's work is devoted to returning blood to the heart from the extremities. Inflation of the bladders also forces blood from the legs and buttocks up the arteries into the aorta. Since the aortic valve, if competent, is closed during diastole, the blood cannot enter the left heart chambers and flows from the aorta into the coronary, carotid and other arteries. An increase in intra-coronary artery pressure of up to 40% was measured during ECP, using tiny pressure transducers positioned in the coronary arteries of humans. Such transducers are manufactured, for instance, by Millar Instruments, Inc. of Houston, Tex.
A number of papers have been published on clinical studies in which ECP devices, made by the owner of the present disclosure, have been shown to be safe and effective in the treatment of Stable (chronic) Angina, Acute Myocardial Infarctions (heart attacks) and Cardiogenic Shock (the most serious complication of a heart attack), and such ECP devices have been cleared for sale by the FDA for the treatment of these conditions, as well as Congestive Heart Failure.
In the treatment of heart attacks, ECP was administered for four hours to force blood around the blockage in one or more of the coronary arteries, relieving the ischemia (oxygen deprivation) caused by the absence of blood flow and reducing the damage to the area of the heart supplied by the blocked artery or arteries. An estimated one million heart attacks occur each year in the United States with a mortality of about 50%.
The repetitive application of ECP, which has been shown to significantly increase intracoronary artery pressure, is thought to cause the release of endogenous (naturally occurring) angiogenic growth factors, resulting in the creation of capillaries and arterioles (angiogenesis) and to restore the elasticity and vitality of the endothelial lining of the arteries of the heart, which usually decline with age. To treat a chronic condition, such as stable angina pectoris (Angina) or Congestive Heart Failure (CHF), ECP is typically administered for a period of one hour, five days a week for seven weeks. It is thought that most or all of the angiogeriic agents stored in the arteries is released within one hour by ECP, and delaying the treatment for a period of time gives the body time to manufacture and restock the depots in the arteries with such growth factors. An estimated 6 million people in the United States suffer from Stable (chronic) Angina, and approximately 2.5 million suffer from CHF.
One present type of ECP device, manufactured by the owner of this application, Cardiomedics, Inc. of Irvine, Calif., consists of a control console, containing a microprocessor, associated electronics and a touch-screen display, a power supply, one or more air compressors, an air reservoir and electrically actuated solenoid valves (“Solenoid Valves”), as known in the art, which are in fluid communication with and, when actuated, release air from the reservoir. Hoses attached to and in fluid communication with the outlets of the Solenoid Valves extend about four to six feet from the Solenoid Valves to bladders disposed in pockets within cuffs, which are fastened about the patient's calves, thighs and buttocks. Such ECP devices weigh about 400 pounds, are portable and can be moved from bed to bed to treat patients, without having to move the patients from their beds.
Other present ECP devices utilize sets of cuffs and bladders about the calves, thighs and buttocks, as described above, but the air reservoir and attached Solenoid Valves are mounted beneath a bed dedicated to the treatment of patients brought to the ECP device. Such other ECP devices are described in U.S. Pat. Nos. 4,753,226; 5,554,103 and 5,997,540. The air compressor and Solenoid Valves associated with such ECP devices may likewise be mounted beneath the bed, or may be housed in a separate enclosure. Locating the air reservoir and attached Solenoid Valves beneath the bed shortens the length of the air hoses to the bladders disposed within the cuffs to about 2 to 3 feet, slightly reducing the inflation time of the bladders and the amount of air lost from the hoses when the cuffs are deflated. However, the weight of such ECP devices is 700 to 1100 pounds, and the lack of portability generally limits their use to ambulatory patients or requires a critically ill patient to be moved on a gurney to the ECP device, moved onto the bed of the ECP device for the ECP treatment, and finally, moved back into his/her bed.
It would be desirable to further reduce the loss of air from the hoses when the bladders are deflated, as well as to not require that patients, particularly critically ill patients, be brought to the ECP device.
In our co-pending application Ser. No. 10/263,954, an advanced ECP device is described, in which lightweight, air pressure actuated valves (“APA Valves”) are attached directly to the individual inlets of bladders disposed within pockets in the cuffs, which are fastened about the calves, thighs and buttocks of the patient. An operating air pressure is maintained in a pneumatic trunk line that extends from a low pressure air reservoir (maintained at up to 10 psi, preferably about 6 psi) and branches into smaller branch pneumatic lines connected to the APA Valves attached to the individual inlets of each of the bladders within the cuffs. The APA Valves, when actuated, admit air into the bladders or allow air to escape through an exhaust port. The APA valves may be spool valves or any other type of valve known in the art.
Air pilot lines are attached to, in fluid communication with, and extend from each of the Solenoid Valves, which are in fluid communication with a high pressure air reservoir (pressurized from about 12 to 30 psi, preferably about 15 to 26 psi). The air pilot lines extend to the APA Valves attached to the inlets of the bladders disposed in the cuffs. By positioning the APA Valves at the inlets of each bladder, pressure is maintained at all times in the trunk and branch pneumatic supply lines. This minimizes the time of inflation of the bladders and significantly reduces the amount of air lost during the exhaust cycle when the bladders are deflated, reducing the size and weight of the compressor(s), reservoir, and power supply of the ECP device. Actuating the APA Valves attached directly to the bladders of the cuffs with air pressure through the air pilot lines, instead of electrically, eliminates the risk of an electrical shock to the patient.
The presence of buttock cuffs in the current ECP devices described above, however, makes it difficult or impossible to insert a catheter into the femoral artery in the patient's groin area, which is required in persons undergoing an angiogram, coronary balloon angioplasty, insertion of an intra-aortic balloon or other cardiac catheterization procedure which may be required in the treatment of the patient. Furthermore, the current ECP devices described above inflate their three sets of cuffs in a fixed sequence, first the calves, then the thighs and finally the buttocks, limiting their use to treating conditions in which such three cuff sequence is desirable. Also, both of the above described ECP devices are programmed to permit compression of the cuffs only during diastole, and the current ECP devices compress the cuffs about both legs of a patient and do not provide for individual cuff inflation, which would be beneficial in the treatment, for example, of an amputee or a person with a broken leg.
As a result, it would be desirable to have an ECP device not subject to the above limitations.
In the treatment of Angina, heart attacks or cardiogenic shock, the patient may suffer from premature ventricular contractions or “PVC's”, which can produce a wide “qrs” interval in the ECG pattern (the time from the end of the “q” wave to the start of the “s” wave), which the microprocessor recognizes and ceases actuation of the Solenoid Valves. Persons with a very low heart rate or an HIS bundle branch block, which is typically treated by implanting a cardiac pacemaker, often produce wide “qrs” intervals in the patient's ECG patterns that are recognized as PVC's by the microprocessor, which causes immediate cessation of actuation of the inflation valves.
It would be desirable to be able to overcome these limitations and provide for a means to enable the operator to over-ride the customary computer program of present ECP devices o treat such patients.
In the treatment of cardiac arrest outside a hospital, cardiopulmonary resuscitation or “CPR” is often applied. The chest is manually compressed by a bystander, who periodically pinches the patient's nose to close the nasal air passages and breathes into the patient's mouth to fill the lungs with air. However, survival from cardiac arrest outside a hospital is very low. This is because manual CPR does not effectively return the blood, which is forced out of the heart by compressing the chest, back to the heart. Also, air breathed into the patient's mouth contains significantly less oxygen and more carbon dioxide than ambient air. Mechanical chest compression devices suffer from the same lack of return of blood to the heart.
When paramedics arrive, a mechanical ventilator, such as the Ambu® MediBag® manufactured by Ambu, Inc. of Linthicum, Md., may be used. The bag is manually squeezed to force ambient, air into the lungs. The paramedics may also apply an electrical shock to the chest to defibrillate and restore the heart to a normal rhythm. However, the weakened heart must continue to work hard to pump blood to the feet and back, and a subsequent cardiac arrest may occur, which may prove fatal.
It would be desirable to have a non-invasive, circulatory assist device that could improve circulation and assist the heart of a person in cardiac arrest, and which could also be used for hours after the patient is resuscitated to reduce the heart's work effort and, perhaps, prevent a subsequent cardiac arrest. The present invention teaches certain benefits in construction and use, which give rise to the objectives described above.
In the treatment of CHF, the patient frequently has a left ventricle ejection fraction less than 40% (55% is normal), due to the inability of the heart to efficiently pump and eject the blood from the main pumping ventricle of the heart. Since ECP increases the flow of blood into the ventricles, excessive pre-loading of the heart can occur in these patients, which could worsen their condition or be fatal. It would be desirable to have an ECP device and a method of use that would prevent this event from occurring.
The present invention fulfills these needs and provides further related advantages as described in the following summary.